Modeliranje turbulentnog dvofaznog toka aero-smeše sprašenog uglja u gorioničkim kanalima sa jednostepenim turbulatorima

The subject of this work is turbulent two-phase flow through air-coal channel(s) of complex geometry. The aim of this work is numerical optimization of fluid flow and coal particle distribution in reconstructed air-coal mixture channels. The single blade turbulator has been used to increase turbulence in the vertical section of an air-coal mixture channel. Standard k-ω turbulent model has been used for modeling turbulence. Lagrangian multiphase model has been used for discrete phase (coal particles) modeling. Although better particle distribution is reached using single blade turbulators, particle concentration in the evaluation section (where plasma generators will be built in) still remains anisotropic. Because uniform coal particle distribution is of great importance for the proper work of plasma generators, other solutions for achieving this goal will be the object of the future analysis.Predmet ovog rada je turbulentno dvofazno strujanje kroz gorioničke kanale aero-smeše sprašenog uglja kompleksne geometrije. Cilj ovog rada je numerička optimizacija strujnog toka i raspodele čestica sprašenog uglja u rekonstruisanim gorioničkim kanalima. Za povećanje turbulencije, u vertikalnom delu gorioničkog kanala aero smeše ugrađen je jednostepeni turbulator. Za modeliranje turbulencije korišćen je standardni k-ω turbulentni model. Lagranžeov pristup je korišćen za modeliranje sekundarne faze (čestica sprašenog uglja). Iako je upotrebom jednostepenih turbulatora postignuta bolja raspodela čestica sprašenog uglja, koncentracija čestica u prelaznom delu (u kome će biti ugrađeni plazma generatori) ostaje neravnomerna. Kako je ravnomerna raspodela čestica sprašenog uglja od esencijalnog značaja za pravilan rad plazma generatora, druga rešenja za postizanje ravnomerne raspodele čestica će biti predmet buduće analize

Review of the Research on the Turbulence in the Laboratory for Thermal Engineering and Energy

Paper gives a review of the most important results of turbulence research achieved by the Laboratory for Thermal Engineering and Energy at the Vinca Insitute of Nuclear Sciences. Paper presents detailed overview of the history of the scientific research provided in the laboratory, from the beginning in the mid-60s to today, pointing out the main reasons initiating the investigations in this field. After the first period, which was mainly devoted to the research of the structure of the turbulence, since the beginning of the 80s, research is mainly oriented to the flows at high temperatures including chemical reactions and to the development and improvement of differential mathematical models as a modern and very efficient tool in the technological development. This research significantly contributed to the development of pulverized coal burners, plasma-chemical reactors, and optimization of pulverized coal fired boilers operating parameters and prediction of the greenhouse gases emissions. Most recent period includes experimental and numerical studies of the coherent structures in turbulent fluid jets, mathematical modeling of various turbulent thermal flow processes including two-phase turbulent flow in the multiphase heat exchangers and mathematical modeling of the atmospheric boundary layer.Turbulence Workshop, Aug 31-Sep 02, 2015, Univ Belgrade, Fac Mech Engn, Belgrade, Serbi

Investigation of Pressure Pulsations in the Furnace and Flue Gas Tract of the Pulverized Coal Combustion Utility Boiler

The paper presents new experimental method developed and new measuring system developed and installed into flame-gas tract of utility boiler. Investigations have been performed at the steam boiler of unit 2 at TPP Ptolemais. Ptolemais, Greece. which suffered from very unstable combustion and great pressure oscillations Experimental method. based on high-speed acquisition system. was developed and used for detection of pressure oscillations and determination of the origin of boiler unstable operation. Signals were obtained from piezoelectric pressure sensors located along the flame-gas tract of the steam boiler and time and frequency domain analysis were used for post processing of collected data. Investigations of the pressure oscillations in boiler gas tract have contributed to reveal origin of the boiler unstable operation. and have been of the great help in establishing proper boiler operatio

Novel Fragmentation Model for Pulverized Coal Particles Gasification in Low Temperature Air Thermal Plasma

New system for start-up and flame support based on coal gasification by low temperature air thermal plasma is planned to supplement current heavy oil system in Serbian thermal power plants in order to decrease air pollutions emission and operational costs. Locally introduced plasma thermal energy heats up and ignites entrained coal particles, thus starting chain process which releases heat energy from gasified coal particles inside burner channel. Important stages during particle combustion, such as particle devolatilisation and char combustion, are described with satisfying accuracy in existing commercial computer fluid dynamics codes that are extensively used as powerful tool for pulverized coal combustion and gasification modeling. However, during plasma coal gasification, high plasma temperature induces strong thermal stresses inside interacting coal particles. These stresses lead to thermal shock and extensive particle fragmentation during which coal particles with initial size of 50-100 mu m disintegrate into fragments of at most 5-10 mu m. This intensifies volatile release by a factor 3-4 and substantially accelerates the oxidation of combustible matter. Particle fragmentation, due to its small size and thus limited influence on combustion process is commonly neglected in modelling. The main focus of this work is to suggest novel approach to pulverized coal gasification under high temperature conditions and to implement it into commercial comprehensive code ANSYS FLUENT 14.0. Proposed model was validated against experimental data obtained in newly built pilot scale direct current plasma burner test facility. Newly developed model showed very good agreement with experimental results with relative error less than 10%, while the standard built-in gasification model had error up to 25%

Fuzzy logic expert system for calculating the parameters of coupled numerical analysis of the fluid and thin-walled structures interaction

U radu su prikazani rezultati numeričkih proračuna interakcije fluid-struktura korišćenjem diskretizacionih numeričkih metoda - metode konačnih elemenata za proračun naponsko-deformacionog stanja zida kanala i metode konačnih zapremina za numerički proračun dinamike fluida. Na osnovu dobijenih rezultata razvijen je fazi ekspertski sistem za procenu izlaznih parametara numeričkog proračuna, prikazane su osnovne karakteristike razvijenog fazi modela i rezultati dobijeni njegovom primenom. Analizirani su uticaji tri ulazna parametra - temperature unutrašnje površine zida kanala, razlike između temperatura unutrašnje i spoljašnje površine zida i faktora koji definiše gustinu numeričkih mreža - na dva izlazna parametra: vrednost pada statičkog pritiska niz struju i vrednost maksimalnih kombinovanih Fon Misesovih napona ostvarenih u strukturi kanala za zadate uslove opterećenja. Na osnovu dobijenih rezultata vidimo da formirani fazi ekspertski sistem može sa zadovoljavajućom tačnošću biti iskorišćen za procenu posmatranih izlaznih veličina, pri znatno kraćem vremenu potrebnom za proračun i uz angažovanje resursa računarskog sistema u značajno manjem obimu.This paper deal with structural deformation of one rectangular, closed, thin walled, steel made, thermally loaded channel and influence of this deformation on the air flow through the channel, recognised as coupled fluid-structure interaction problem. The geometrically non-linear deformation of thermally loaded channel was solved using commercial finite-element analysis software ANSYS. The unsteady Navier-Stokes equations in their conservation form defining fluid flow are solved using commercial computer fluid dynamics software ANSYS CFX. A fuzzy logic-based expert system has been developed to predict some results of structural and fluid flow numerical simulation instead of directly evaluating it by a time-consuming software coupling of finite-element and computer fluid dynamics numerical analysis. Three input parameters, namely temperature of channel inner walls, difference in temperature of inner and outer surface of channel wall, and factor of mesh size, are varied while solving the fluid-structure interaction problem. A pressure drop downstream the flow was considered as a computer fluid dynamics output parameter of importance, while Von Misses maximum stresses were an finite-element analysis output parameter observed. The developed FLES can predict the results of finite-element and computer fluid dynamics analysis, a pressure drop and Von Misses maximum stresses respectively, within a reasonable accuracy limit and at lower computation cost compared to the finite-element, and CFD computer fluid dynamics packages combined into series of multi-physics analyses

Fuzzy logic expert system for calculating the parameters of coupled numerical analysis of the fluid and thin-walled structures interaction

U radu su prikazani rezultati numeričkih proračuna interakcije fluid-struktura korišćenjem diskretizacionih numeričkih metoda - metode konačnih elemenata za proračun naponsko-deformacionog stanja zida kanala i metode konačnih zapremina za numerički proračun dinamike fluida. Na osnovu dobijenih rezultata razvijen je fazi ekspertski sistem za procenu izlaznih parametara numeričkog proračuna, prikazane su osnovne karakteristike razvijenog fazi modela i rezultati dobijeni njegovom primenom. Analizirani su uticaji tri ulazna parametra - temperature unutrašnje površine zida kanala, razlike između temperatura unutrašnje i spoljašnje površine zida i faktora koji definiše gustinu numeričkih mreža - na dva izlazna parametra: vrednost pada statičkog pritiska niz struju i vrednost maksimalnih kombinovanih Fon Misesovih napona ostvarenih u strukturi kanala za zadate uslove opterećenja. Na osnovu dobijenih rezultata vidimo da formirani fazi ekspertski sistem može sa zadovoljavajućom tačnošću biti iskorišćen za procenu posmatranih izlaznih veličina, pri znatno kraćem vremenu potrebnom za proračun i uz angažovanje resursa računarskog sistema u značajno manjem obimu.This paper deal with structural deformation of one rectangular, closed, thin walled, steel made, thermally loaded channel and influence of this deformation on the air flow through the channel, recognised as coupled fluid-structure interaction problem. The geometrically non-linear deformation of thermally loaded channel was solved using commercial finite-element analysis software ANSYS. The unsteady Navier-Stokes equations in their conservation form defining fluid flow are solved using commercial computer fluid dynamics software ANSYS CFX. A fuzzy logic-based expert system has been developed to predict some results of structural and fluid flow numerical simulation instead of directly evaluating it by a time-consuming software coupling of finite-element and computer fluid dynamics numerical analysis. Three input parameters, namely temperature of channel inner walls, difference in temperature of inner and outer surface of channel wall, and factor of mesh size, are varied while solving the fluid-structure interaction problem. A pressure drop downstream the flow was considered as a computer fluid dynamics output parameter of importance, while Von Misses maximum stresses were an finite-element analysis output parameter observed. The developed FLES can predict the results of finite-element and computer fluid dynamics analysis, a pressure drop and Von Misses maximum stresses respectively, within a reasonable accuracy limit and at lower computation cost compared to the finite-element, and CFD computer fluid dynamics packages combined into series of multi-physics analyses

Pljevlja lignite carbon emission charateristics

The anthropogenic emission of GHG especially CO has to be limited and reduced due to their impact on global warming and climate change. Combustion of fossil fuels in the energy sector has a dominant share in total GHG emissions. In order to reduce GHG emission, European Union established a scheme for GHG allowance trading within the community, and the implementation of the European Union emission trading scheme, which is a key to GHG reduction in a cost-effective way. An important part of emission trading scheme is prescribed methodology for monitoring, reporting, and verification of the emission of GHG including characterization of the local fuels combusted by the energy sector. This paper presents lignite characteristics from open-pit mine Borovica-Pljevlja, which has highest coal production in Montenegro (>1.2 Mt per year), including evaluation of its carbon emission factor based on the laboratory analysis of 72 coal samples. Testing of the samples included proximate and ultimate analysis, as well as, net calorific value determination. In accordance with the obtained results, linear correlations between net calorific value and combustible matter content, carbon content and combustible matter content, hydrogen content and combustible matter content, carbon content and net calorific value, were established. Finally, the non-linear analytical correlation between carbon emission factor and net calorific value for Pljevlja lignite was proposed, as a base for the precise calculation of CO emission evaluation

Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for thermal engineering and energy: Part B

Paper presents short review of research problems, applied methods for solving problems and main results obtained by the researchers in Laboratory for Ther-mal Engineering and Energy (LTE) of the "Vinca" Institute of Nuclear Sciences, Belgrade, Serbia dealing with pulverized coal combustion processes and tech-nologies for reduction of pollutions problems at thermal power plants in a period since 2000. The presented results were published in numerous studies realized for different users, Ph. D., Masters, and Specialist thesis, in international and domestic scientific journals and monographs, presented at numerous internation-al and domestic scientific conferences, etc. Presented research projects and re-sults of applied research projects realized at pulverized coal combustion thermal power plants clearly show that LTE team was involved in key activities of reha-bilitation and modernization, including implementation of best available technol-ogies for pollution reduction at thermal power plants, in the region of South East Europe

Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for thermal engineering and energy-Part A

The paper presents an overview of the results of the investigations of the process-es that take place in pulverized coal combustion boilers and power plants which, in a longer period of time, were realized in the Laboratory for Thermal Engineer-ing and Energy of the "Vinca" Institute of Nuclear Sciences. The presented re-sults were published in numerous studies realized for different users, Ph. D., M. Sc., and specialist thesis, in international and domestic scientific journals and monographs, presented at numerous international and domestic scientific meet-ings, etc. The main goal of the paper is to chronologically present the results of domestic research that at one time were at an enviable international level, with concrete practical applications for domestic users. This is especially important to contrast the present situation when domestic research in this area is scarce and when the energy sector relies practically only on imported technologies and for-eign consultancy. © 2019 Society of Thermal Engineers of Serbia.Corrigendum: Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for Thermal Engineering and Energy-Part A (Thermal Science, 23, Suppl. 5 (2019) (S1587-S1609)) DOI:[https://doi.org/10.2298/TSCI200127032E] (2020) Thermal Science, 24, p. 657

Assessment Results of Fluid-Structure Interaction Numerical Simulation Using Fuzzy Logic

A fuzzy approximation concept is applied in order to predict results of coupled computational structure mechanics and computational fluid dynamics while solving a problem of steady incompressible gas flow through thermally loaded rectangular thin-walled channel. Channel wall deforms into wave-type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. A set of fluid-structure interaction numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall, and numerical grid density. The unsteady Navier-Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The structural model is solved by finite element method including geometric and material non-linearities. The implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. Results of numerical analysis indicate that gravity and pressure distribution inside the channel contributes to triggering the shape of deformation. In the inverse problem, the results of fluid-structure interaction numerical simulations formed a database of input variables for development fuzzy logic based models considering downstream pressure drop and maximum stresses as the objective functions. Developed fuzzy models predicted targeting results within a reasonable accuracy limit at lower computation cost compared to series of fluid-structure interaction numerical calculations. Smaller relative difference were obtained when calculating the values of pressure drop then maximal stresses indicating that transfer function influence on output values have to be additionally investigated